The present invention relates to methods of making microelectronic assemblies incorporating a plurality of microelectronic elements and separating the assemblies into individual units.
Microelectronic elements, such as semiconductor chips or wafers, are typically packaged and assembled with a microelectronic component to facilitate connection to external circuitry. It is known to assemble a flexible dielectric sheet with microelectronic elements to form a microelectronic package. As disclosed in certain embodiments of commonly assigned U.S. Pat. No. 5,518,964, a microelectronic component has a plurality of leads with tip ends and terminal ends. The tip ends of each lead are bonded to contacts on a semiconductor wafer incorporating a plurality of individual chips. The wafer and microelectronic component are moved in relation to one another so as form a generally S-shaped lead extending between the wafer and the microelectronic component. A flowable dielectric material is introduced between the microelectronic component and the wafer so as to form a dielectric layer between the component and the wafer. After curing the flowable material to form a dielectric layer, the wafer, the microelectronic component and the dielectric layer are simultaneously severed by sawing along lines so as to divide the assembly into individual microelectronic units.
Various methods are used for separating a wafer into individual microelectronic devices. In one method, a semiconductor wafer is secured in a vacuum package and a roller is used to break the wafer into individual units along scribe lines. The individual units are held in place by the vacuum package as the package is placed in a heated press for adhering the microelectronic devices to the lower layer of the package. An upper layer of the package is removed so that the lower layer of the package may be stretched in a vacuum mold, with the lower layer of the package carrying the individual microelectronic devices.
In other known methods, a wafer is secured to a sapphire disk with a layer of wax, and the individual chips of the wafer are separated by separation etching. The individual chips are transferred from the sapphire disk to a glass plate by a wire screen. The wire screen is then removed from the chips after adhering the chips to the glass plate.
In still other known methods, a semiconductor wafer is broken into individual units and then glued to a membrane. The wafer is first secured to a disk, which is removed after the units are glued to the membrane. The units are then transferred to a receiving member having a stretched membrane. The individual units are attached to the stretched membrane. A plurality of transferring and cleaning steps are required in this method.
In spite of the above advances, there remains a need for improved methods of making microelectronic assemblies.